In immuno-chemical analyses, such as enzyme immuno assay (EIA) or fluorescence immuno assay (FIA), free labelled antibody or antigen must in most cases be separated from the labelled antigen-antibody complex. This is commonly accomplished by means of a solid phase that can be present e.g. in the form of a particle or a surface, either the free labelled component or the complex being retained by the solid phase on the basis of molecular size, adsorption or different types of chemical (including immuno-chemical) bonding. Typical for such analyses today is that they require several liquid processing steps for carrying out the reaction sequence. For that reason most immuno-chemical analyses are, with the technique used today, limited to laboratories having trained personnel.
By means of the device according to the invention it has been shown to be possible to considerably facilitate and simplify the processing and operational steps of analyses of the above-mentioned type so that they can be performed also by non-trained personnel, e.g. doctors and nurses in offices and hospitals. The device is even simple enough to be handled in many cases by the patient himself. Furthermore, an important factor in the last-mentioned connection is that due to its very simple construction the device can also be made very inexpensively, which means that it might achieve a wide spread commercial use, at least for some qualitative and semi-quantitative tests where certain states of illness can be confirmed by the patient himself before there is a need for any consultation with a doctor.
However, as was mentioned above the device is in no way limited to use in connection with immuno-chemical analyses, but for the sake of simplicity and for a better understanding it will still be described more in detail below in connection therewith. In this context it could also be added that the described analyses and the reagents utilized in connection therewith are well known and are disclosed in numerous references. Thus it should not be necessary to repeat details thereabout here since these can be found in suitable literature within the field. For examples of techniques used within the field of immuno-chemical analyses reference is made to the techniques described in Swedish Patent Application Ser. No. 8205751-4. However, nor is said literature reference intended to be in an way exhaustive within this field.
For the purpose of elucidating the invention even more as well as the technical field to which it relates it should also be added that it bears no relation to those numerous simple diffusion devices which are disclosed in the literature, i.e. where a sample either passively or by means of capillary forces is allowed to diffuse through one or more chemically active layers. Examples of references which disclose devices of this kind are U.S. Pat. No. 3,511,608, GB Pat. No. 2,031,583, EP No. 64,392, U.S. Pat. No. 4,066,403 and EP No. 51,183. As far as these are concerned it should be pointed out that those overlapping segments which are disclosed in U.S. Pat. No. 3,511,608 or those foldable sheets which are disclosed in GB Pat. No. 2,031,583 and EP No. 64,392 relate to possible manufacturing methods for diffusion devices but have no functional purpose for the execution of the analysis, during which time said segments or sheets are permanently connected to one another in one single piece. Although there in e.g. GB Pat. No. 2,031,583 and EP No. 64,392 are flaps which are foldable to the user, these flaps are only used as protective lids or covers and do not take part in the chemical or analytical process.
The device according to the invention differs essentially from the above-mentioned devices through the fact that it is not based upon any diffusion principle. Instead the analysis is performed step by step as in the laboratory. The novelty of the concept is that liquid samples and reagents need not be transferred between test tubes or test cups by repeated pipetting operations. Instead samples, reagents and even a washing function are contained on surfaces of the device. Transfer of samples or reagents between the surfaces is accomplished by a simple folding action. This offers considerable advantages over multilayer diffusion elements of the type that are disclosed in e.g. U.S. Pat. No. 4,066,403 and EP No. 51,183. The user retains full control of the timing of the different reaction steps, while the timing for diffusion devices of the multilayer type can be varied only by the manufacturer by choice of layer material and even then merely to a limited extent. Moreover, the device according to the invention can be utilized for the analysis of most substances without a need for any major modifications of its basic structure or design. In immuno-chemical analyses there are substances of extremely varying size, from drugs having a molecular weight of not more than 500 to whole cells and bacteria which are a billion times larger. As substances of different size diffuse at different rates, diffusion devices therefore have an additional drawback in that it is necessary to adjust the types of layers for each kind of analyte. Finally, it should be added that the method of manufacture and the storage properties of the device according to the invention are based on established technology while these factors have proven to be difficult to master in practice for immuno-chemical diffusion devices of the multilayer type.